In October 1939, barely a month after the outbreak of World War II, the battleship HMS Royal Oak was lying at anchor at Scapa Flow, fully armed and carrying 3400 tons of fuel oil, when she was sunk by a German U-boat.

She rolled over and sank within 13 minutes, with the loss of 833 officers and men and since then has lain virtually undisturbed, in 30 metres of water, as a designated war grave.

Oil has been seeping from the vessel since it was sunk, but it had been dispersing gradually and had posed no threat to the environment until 1996, when a significant amount of oil was washed ashore.

Orkney Islands Council approached the Royal Navy with a view to solving the problem. They estimated that 900 to 1800 tonnes of oil remained onboard and that it might leak out for another fifteen years.

The chosen solution was to collect the oil and bring it to the surface for safe disposal. A stainless steel 'tent', measuring 10m long by 4.8m deep, with a capacity of 50 cubic metres and weighing around 4 tonnes was designed as a collecting device.

The contract for its construction was awarded to Narvida. If it is not damaged, the structure should last for 50-60 years - well past the time during which the seepage is likely to continue. A dedicated barge moored adjacent to the wreck collects the oil and delivers it to the Flotta oil terminal in Orkney.